Chap boots are a form of footwear

Footwear

Footwear consists of garments worn on the feet, for fashion, protection against the environment, and adornment. Being barefoot is commonly associated with poverty, but some cultures chose not to wear footwear at least in some situations....

. They are tall boots

Boot

A boot is a type of footwear but they are not shoes. Most boots mainly cover the foot and the ankle and extend up the leg, sometimes as far as the knee or even the hip. Most boots have a heel that is clearly distinguishable from the rest of the sole, even if the two are made of one piece....

 which cover the whole leg

Human leg

The human leg is the entire lower extremity or limb of the human body, including the foot, thigh and even the hip or gluteal region; however, the precise definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle.Legs are used for standing,...

 up to the crotch

Crotch

The term crotch may be used to describe the region of an object where it splits into two or more limbs. This can include trees, animals, buildings, in wiring diagrams, etc....

, with a strap coming up from far side. These straps contain a loop of material from which a belt

Belt (clothing)

A belt is a flexible band or strap, typically made of leather or heavy cloth, and worn around the waist. A belt supports trousers or other articles of clothing.-History:...

 is poked through and used to hold the boots up. Thus the boots act similarly to a pair of chaps

Chaps

Chaps are sturdy coverings for the legs consisting of leggings and a belt. They are buckled on over trousers with the chaps' integrated belt, but unlike trousers they have no seat and are not joined at the crotch. They are designed to provide protection for the legs and are usually made of leather...

. Such boots are often seen as part of boot fetishism.